Electric warming blanket having optimized temperature zones
An electric heating blanket system includes a flexible sheet-like heating element having a substantially uniform watt density output across a surface area thereof, when the heating element is electrically powered. A temperature sensor is coupled to the heating element at a location where the heating element will be in conductive contact with a body when the blanket is draped over the body. The system further includes a temperature controller coupled to the temperature sensor, and an electric power source coupled to the heating element and to the temperature controller, the power source being controlled to provide the watt density output for the heating element according to a temperature sensed by the sensor.
Latest Augustine Temperature Management LLC Patents:
The present application claims priority to provisional application Ser. No. 60/722,106 entitled: ELECTRIC WARMING BLANKET INCLUDING TEMPERATURE ZONES AUTOMATICALLY OPTIMIZED, and to provisional application Ser. No. 60/722,246, entitled: HEATING BLANKET, both of which were filed on Sep. 29, 2005, and both of which are incorporated by reference in their entireties herein.
RELATED APPLICATIONSThe present application is related to the following commonly assigned utility patent applications, all of which are filed concurrently herewith and all of which are hereby incorporated by reference in their entireties: A) NOVEL DESIGNS FOR HEATING BLANKETS AND PADS, Practitioner Ser. No. 11/537,179B) TEMPERATURE SENSOR ASSEMBLIES FOR AN ELECTRIC WARMING BLANKET, Practitioner Ser. No. 11/537,189; C) FLEXIBLE HEATING ELEMENT CONSTRUCTION, Practitioner Ser. No. 11/537,199; D) BUS BAR ATTACHMENTS FOR FLEXIBLE HEATING ELEMENTS, Practitioner Ser. No. 11/537,212; and E) BUS BAR INTERFACES FOR FLEXIBLE HEATING ELEMENTS, Practitioner Ser. No. 11/537,222.
TECHNICAL FIELDThe present invention is related to heating or warming blankets and more particularly to heating blankets including electrical heating elements.
BACKGROUNDIt is well established that surgical patients under anesthesia become poikilothermic. This means that the patients lose their ability to control their body temperature and will take on or lose heat depending on the temperature of the environment. Since modern operating rooms are all air conditioned to a relatively low temperature for surgeon comfort, the majority of patients undergoing general anesthesia will lose heat and become clinically hypothermic if not warmed.
Over the past 15 years, forced-air warming (FAW) has become the “standard of care” for preventing and treating the hypothermia caused by anesthesia and surgery. FAW consists of a large heater/blower attached by a hose to an inflatable air blanket. The warm air is distributed over the patient within the chambers of the blanket and then is exhausted onto the patient through holes in the bottom surface of the blanket.
Although FAW is clinically effective, it suffers from several problems including: a relatively high price; air blowing in the operating room, which can be noisy and can potentially contaminate the surgical field; and bulkiness, which, at times, may obscure the view of the surgeon. Moreover, the low specific heat of air and the rapid loss of heat from air requires that the temperature of the air, as it leaves the hose, be dangerously high—in some products as high as 45° C. This poses significant dangers for the patient. Second and third degree burns have occurred both because of contact between the hose and the patient's skin, and by blowing hot air directly from the hose onto the skin without connecting a blanket to the hose. This condition is common enough to have its own name—“hosing.” The manufacturers of forced air warming equipment actively warn their users against hosing and the risks it poses to the patient.
To overcome the aforementioned problems with FAW, several companies have developed electric warming blankets. However, these electric blankets have a number of inadequacies, examples of which include, a stiffness prohibiting a draping of the blankets over a patient that results in less than optimal conductive heat transfer to the patient, and a non-uniform watt density output across a surface area of the blankets.
The following drawings are illustrative of particular embodiments of the present invention and therefore do not limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description. Embodiments of the present invention will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements.
The following detailed description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the following description provides practical illustrations for implementing exemplary embodiments of the present invention. Examples of constructions, materials, dimensions, and manufacturing processes are provided for selected elements, and all other elements employ that which is known to those of skill in the field of the invention. Those skilled in the art will recognize that many of the examples provided have suitable alternatives that can be utilized. The term ‘blanket’, used to describe embodiments of the present invention, may be considered to encompass heating blankets and pads.
According to an exemplary embodiment, a conductive fabric for heating element 10 comprises a non-woven polyester having a basis weight of approximately 130 g/m2 and being 100% coated with polypyrrole (available from Eeonyx Inc., Pinole, Calif.); the coated fabric has an average resistance, for example, determined with a four point probe measurement, of approximately 15-20 ohms per square, at about 48 volts, which is suitable to produce the preferred watt density of 0.2 to 0.4 watts/sq. in. for surface areas of heating element 10 having a width, between bus bars 15, in the neighborhood of about 20 inches. Such a width is suitable for a lower body heating blanket, an exemplary embodiment of which will be described below. A resistance of such a conductive fabric may be tailored for different widths between bus bars (wider requiring a lower resistance and narrower requiring a higher resistance) by increasing or decreasing a surface area of the fabric that can receive the conductive coating, for example by increasing or decreasing the basis weight of the fabric.
A flexibility of blanket subassembly 100, provided primarily by flexible heating element 10, and optionally enhanced by the incorporation of flexible bus bars, allows blanket subassembly 100 to conform to the contours of a body, for example, all or a portion of a patient undergoing surgery, rather than simply bridging across high spots of the body; such conformance may optimize a conductive heat transfer from element 10 to a surface of the body. However, as illustrated in
The uniform watt-density output across the surface areas of preferred embodiments of heating element 10 translates into a uniform heating of the surface areas, but not necessarily a uniform temperature. At locations of heating element 10 which are in conductive contact with a body acting as a heat sink, for example, body 16, the heat is efficiently drawn away from heating element 10 and into the body, for example by blood flow, while at those locations where element 10 does not come into conductive contact with the body, for example lateral portions 11, 12 as illustrated in
According to embodiments of the present invention, zones of heating element 10 may be differentiated according to whether or not portions of element 10 are in conductive contact with a body, for example, a patient undergoing surgery. In the case of conductive heating, gentle external pressure may be applied to a heating blanket including heating element 10, which pressure forces heating element 10 into better conductive contact with the patient to improve heat transfer. However, if excessive pressure is applied the blood flow to that skin may be reduced at the same time that the heat transfer is improved and this combination of heat and pressure to the skin can be dangerous. It is well known that patients with poor perfusion should not have prolonged contact with conductive heat in excess of approximately 42° C. 42° C. has been shown in several studies to be the highest skin temperature, which cannot cause thermal damage to normally perfused skin, even with prolonged exposure. (Stoll & Greene, Relationship between pain and tissue damage due to thermal radiation. J. Applied Physiology 14(3):373-382. 1959. and Moritz and Henriques, Studies of thermal injury: The relative importance of time and surface temperature in the causation of cutaneous burns Am. J. Pathology 23:695-720, 1947) Thus, according to certain embodiments of the present invention, the portion of heating element 10 that is in conductive contact with the patient is controlled to approximately 43° C. in order to achieve a temperature of about 41-42° C. on a surface a heating blanket cover that surrounds element 10, for example, a cover or shell 20 which will be described below in conjunction with
With further reference to
According to some embodiments of the present invention, shell 20 includes top and bottom sheets extending over either side of assembly 250; the two sheets of shell 20 are coupled together along a seal zone 22 that extends about a perimeter edge 2000 of blanket 200, and within perimeter edge 2000 to form zones, or pockets, where a gap exists between the two sheets. According to an exemplary embodiment of the present invention, shell 20 comprises a nylon fabric having an overlay of polyurethane coating to provide waterproofing; the coating is on at least an inner surface of each of the two sheets, further facilitating a heat seal between the two sheets, for example, along seal zone 22, according to preferred embodiments. It should be noted that, according to alternate embodiments of the present invention, a covering for heating assemblies, such as heating assembly 250, may be removable and, thus, include a reversible closure facilitating removal of a heating assembly therefrom and insertion of the same or another heating assembly therein.
Returning now to
In the foregoing detailed description, the invention has been described with reference to specific embodiments. However, it may be appreciated that various modifications and changes can be made without departing from the scope of the invention as set forth in the appended claims. Although embodiments of the invention are described in the context of an operating environment, it is contemplated that some embodiments of the invention may be used in other environments.
Claims
1. A method of warming a patient during surgery, the method comprising:
- providing a heating blanket comprising a flexible sheet-like heating element having generally uniform electrical resistance per unit area such that the heating element produces a substantially uniform watt density output across a surface area thereof when the heating element is electrically powered, the heating element including a first side and a second side opposite the first side, the first side having a temperature sensor coupled thereto at a location that defines a first temperature zone of the heating element;
- placing the heating blanket over a patient, such that the second side of the heating element faces toward the patient, the first temperature zone of the heating element is in thermal conductive contact with the patient, and a second temperature zone of the heating element is alongside the patient but not in thermal conductive contact with the patient;
- monitoring a temperature of the first temperature zone of the heating element, as sensed by the temperature sensor, after the blanket is placed over the patient; and
- controlling electric power to the heating element, according to the monitored temperature of the first temperature zone; and
- maintaining a first temperature of the first temperature zone only, the maintained first temperature being lower than a second temperature of the second temperature zone, after the blanket is placed over the patient.
2. The method of claim 1, further comprising extending, from the heating element, an unheated flap of the heating blanket along a side of the patient to enclose that side of the patient.
3. The method of claim 1, wherein the flexible sheet-like heating element comprises an electrically conductive fabric.
4. The method of claim 1, wherein the flexible sheet-like heating element comprises a nonconductive layer coated with an electrically conductive material.
5. The method of claim 4, wherein the nonconductive layer comprises woven polyester and the conductive material comprises polypyrrole.
6. The method of claim 1, wherein the flexible sheet-like heating element comprises a fabric incorporating closely spaced electrically conductive elements.
7. The method of claim 1, wherein the substantially uniform watt density is no greater than approximately 0.5 watts per square inch.
3808403 | April 1974 | Kanaya et al. |
3839621 | October 1974 | Hariu |
3900654 | August 1975 | Stinger |
3936661 | February 3, 1976 | Furuishi et al. |
4061898 | December 6, 1977 | Murray et al. |
4149066 | April 10, 1979 | Niibe |
4479795 | October 30, 1984 | Mustacich et al. |
4534886 | August 13, 1985 | Kraus et al. |
4626664 | December 2, 1986 | Grise |
4719335 | January 12, 1988 | Batliwalla et al. |
4764665 | August 16, 1988 | Orban et al. |
4798936 | January 17, 1989 | Johnson, Sr. |
4912306 | March 27, 1990 | Grise et al. |
5008515 | April 16, 1991 | McCormack |
5010233 | April 23, 1991 | Henschen et al. |
5023433 | June 11, 1991 | Gordon |
5380580 | January 10, 1995 | Rogers et al. |
5422462 | June 6, 1995 | Kishimoto |
5443056 | August 22, 1995 | Smith et al. |
5773275 | June 30, 1998 | Anderson et al. |
5817145 | October 6, 1998 | Augustine et al. |
5824996 | October 20, 1998 | Kochman et al. |
5928274 | July 27, 1999 | Augustine |
5964792 | October 12, 1999 | Augustine |
5974605 | November 2, 1999 | Dickerhoff et al. |
5986243 | November 16, 1999 | Campf |
6078026 | June 20, 2000 | West |
6093910 | July 25, 2000 | McClintock et al. |
6172344 | January 9, 2001 | Gordon et al. |
6184496 | February 6, 2001 | Pearce |
6235049 | May 22, 2001 | Nazerian |
6373034 | April 16, 2002 | Rock et al. |
6403935 | June 11, 2002 | Kochman et al. |
6483087 | November 19, 2002 | Gardner et al. |
6582456 | June 24, 2003 | Hand et al. |
6770848 | August 3, 2004 | Haas et al. |
6770854 | August 3, 2004 | Keane |
6839922 | January 11, 2005 | Foggett et al. |
6933469 | August 23, 2005 | Ellis et al. |
6974935 | December 13, 2005 | O'Grady |
7022950 | April 4, 2006 | Haas et al. |
7053344 | May 30, 2006 | Surjan et al. |
20020005398 | January 17, 2002 | Gillner et al. |
20020117495 | August 29, 2002 | Kochman et al. |
20050016982 | January 27, 2005 | Campf et al. |
586745 | March 1947 | GB |
- EeonTexTM Conductive Textiles, Product Details, www.eeonyx.com/prodte.html, Sep. 19, 2006, pp. 1-5.
- U.S. Appl. No. 11/537,179, Office Action dated Aug. 16, 2007, 6 pages.
- U.S. Appl. No. 11/537,179, Office Action dated Dec. 31, 2007, 18 pages.
- U.S. Appl. No. 11/537,179, Final Office Action dated Aug. 7, 2008, 15 pages.
- U.S. Appl. No. 11/537,189, Office Action dated Aug. 16, 2007, 5 pages.
- U.S. Appl. No. 11/537,189, Office Action dated Dec. 28, 2007, 12 pages.
- U.S. Appl. No. 11/537,189, Final Office Action dated Aug. 6, 2008, 12 pages.
- U.S. Appl. No. 11/537,212, Office Action dated Feb. 23, 2007, 5 pages.
- U.S. Appl. No. 11/537,212, Office Action dated Jul. 18, 2007, 7 pages.
- U.S. Appl. No. 11/537,212, Final Office Action dated Mar. 17, 2008, 8 pages.
- U.S. Appl. No. 111537,212, Notice of Allowance dated Sep. 26, 2008, 6 pages.
- U.S. Appl. No. 111537,222, Office Action dated Feb. 23, 2007, 8 pages.
- U.S. Appl. No. 11/537,222, Office Action dated Jul. 18, 2007, 6 pages.
- U.S. Appl. No. 11/537,222, Final Office Action dated May 1, 2008, 7 pages.
- PCT Application No. PCT/US2006/038232, International Search Report and Written Opinion, dated Jan. 23, 2007, 11 pages.
- PCT Application No. PCT/US2006/038231, International Search Report and Wirtten Opinion, dated Aug. 20, 2007, 8 pages.
- U.S. Appl. No. 11/537,179, Office Action, dated May 27, 2009, 17 pages.
- U.S. Appl. No. 11/537,189, Office Action, dated Apr. 28, 2009, 14 pages.
- U.S. Appl. No. 11/537,222, Final Office Action, dated Nov. 12, 2008, 7 pages.
- U.S. Appl. No. 11/537,179, Office Action, dated Nov. 18, 2009, 11 pages.
- U.S. Appl. No. 11/537,189, Final Office Action, dated Oct. 27, 2009, 20 pages.
Type: Grant
Filed: Sep 29, 2006
Date of Patent: Dec 14, 2010
Patent Publication Number: 20070068930
Assignee: Augustine Temperature Management LLC (Eden Prairie, MN)
Inventors: Scott D. Augustine (Bloomington, MN), Randall C. Arnold (Minnetonka, MN), Rudolf A. Deibel (Eden Prairie, MN), Scott A. Entenman (St. Paul, MN), Keith J. Leland (Medina, MN), Thomas F. Neils (Minneapolis, MN)
Primary Examiner: Tu B Hoang
Assistant Examiner: Vinod D Patel
Attorney: Fredrikson & Byron, P.A.
Application Number: 11/537,173
International Classification: H05B 3/34 (20060101);